Many oilfield operations expose wellhead equipment at the surface of a subterranean wellbore to extreme conditions—examples of such oilfield operations include cementing, acidizing, injecting, fracturing, and/or gravel packing of the wellbore. Isolation tools are available that attempt to protect wellhead equipment from excessive pressures, temperatures, and flow rates encountered during oilfield operations, but these isolation tools are often insufficient to handle extreme duty cycles. For example, during fracturing of the wellbore, the wellhead equipment may be subject to a fluid pressure of up to 20,000 psi or more. Some isolation tools are configured to position and secure a mandrel within a wellhead, which mandrel includes a packoff assembly adapted to isolate the wellhead from fluid flowing through the mandrel to and from the wellbore. However, the high pressures and flow rates encountered during wellbore fracturing operations often cause packoff assemblies to “lift-off” from a sealing surface, allowing the fracturing fluid or slurry to leak or blow by the packoff assembly into the wellhead equipment. For this reason (among others), existing isolation tools are susceptible to blowouts (i.e., the uncontrolled release of oil and/or gas from the wellbore). To make matters worse, if a blowout does occur, there is no simple way to stop the blowout using existing isolation tools. Therefore, what is needed is an apparatus, system, or method that addresses one or more of the foregoing issues, and/or one or more other issues.